Spatial Distributions of Riverine and Marine Dissolved Organic Carbon in the Western Arctic Ocean: Results From the 2018 Korean Expedition

Abstract

Seasonal primary production and river discharge increases in the Arctic Ocean exert a significant influence on the dissolved organic carbon (DOC) cycle. To improve our knowledge of the spatial heterogeneity of DOC source and concentration in the rapidly changing Arctic Ocean, we investigated the distributions of riverine and marine DOC in the western Arctic Ocean during the summer of 2018. Although the surface bulk DOC concentration indicated no clear distinction in its distribution between the Chukchi Borderland (CBL)/northern Chukchi Sea (NCS) and East Siberian Sea (ESS)/Mendeleyev Ridge (MR) regions, the estimated riverine DOC concentration (28 ± 4.2 μM C) and its contribution (40 ± 5.7%) in the surface layer of the CBL/NCS region were higher than those (19 ± 5.6 μM C and 26 ± 8.5%) in the ESS/MR region, which was attributed to the accumulation of freshwater, strong stratification, and a longer residence time in the CBL/NCS region. In contrast, although marine DOC was the dominant DOC component in both the CBL/NCS and ESS/MR regions, the higher marine DOC concentration (54 ± 8.1 μM C) and its contribution (73 ± 8.2%) in the East Siberian shelf/slope region were consistent with high bacterial abundance, which was associated with extremely high surface phytoplankton blooms sustained by nutrient supply from the deep layer, suggesting that the supply of bioavailable DOC resulted in active bacterial activities. Overall, the spatial differences in water properties between the two regions had large influences on the regional distributions of riverine and marine DOC.

Characterization and source of fluorescent dissolved organic matter in the Western Arctic Ocean: new insights from the 2019 summer study

“…Given the ongoing climate change in the western Arctic Ocean, water mass structures are expected to be modified (Polyakov et al, 2017;Polyakov et al, 2020). Shoaling of the upper halocline layer, observed in our study region (Jung et al, 2021a;Jung et al, 2022), had the potential to supply humic-like FDOM to the euphotic zone. Thus, photodegradation of the humic-like FDOM, combined with the supply of inorganic nutrients to the surface layer, could enhance marine primary productivity in the western Arctic Ocean.…”

“…For the CBL and ESS, DOC river was set to be 175 mM C, corresponding to zerosalinity (100% river water) DOC value, obtained from the relationship between DOC and sea ice meltwater-corrected S in these regions (Figure S1). Details underlying the choice of DOC river in our study regions can be found in the publications by Jung et al (2021b) and Jung et al (2022).…”

Glucose Enhances Salinity-Driven Sea Spray Aerosol Production in Eastern Arctic Waters

“…A fraction of fresh DOC has biological origins from phytoplankton cells via physiological exudates, zooplankton grazing, and viral lysis . These processes release labile DOC that is bioavailable to heterotrophic microorganisms. , More refractory DOC is typically derived from terrestrial sources. , DOC is also released from sea-ice melt. , Concerning organic nitrogen, in studies around the Antarctic Peninsula, Dall′Osto et al , and Rinaldi et al suggested that DON can leak from melting sea ice and being incorporated into marine aerosols once transformed into methylamines, although the involved biological and chemical processes are poorly understood. However, we did not find any strong positive correlation between DOC or DON and SSA number concentration or aerosol size distribution (Table and Figures C and ), probably because the DOM components potentially active in changing air bubble properties and aerosol production were just a minor proportion of the total DOC and DON pools.…”

“… 80 , 81 More refractory DOC is typically derived from terrestrial sources. 82 , 83 DOC is also released from sea-ice melt. 47 , 84 Concerning organic nitrogen, in studies around the Antarctic Peninsula, Dall′Osto et al 54 , 85 and Rinaldi et al 86 suggested that DON can leak from melting sea ice and being incorporated into marine aerosols once transformed into methylamines, although the involved biological and chemical processes are poorly understood.…”